The present invention relates generally to the field of switches and more particularly to those types of switches that are actuated by acceleration forces.
Various types of acceleration responsive switches have been described in the prior art. For instance, U.S. Pat. No. 5,828,138 by McIver et al. discloses an acceleration switch wherein an inertial mass member is held in a holding position by an electrostatic force until the acceleration forces exerted upon it causes the inertial mass member to deflect to an actuated position. U.S. Pat. No. 5,600,109 by Mizutani et al. discloses an acceleration switch wherein acceleration forces cause an inertia ball to bridge one or more contacts located radially around the ball.
The present invention is a switch that changes between a first condition and a second condition in response to acceleration forces exerted upon it. The switch includes a material that changes from a high viscosity (first state) to a low viscosity (second state) when subjected to acceleration forces. The change in states results in the switch changing between its first and second conditions.
One embodiment of the invention is a normally-open, electrical switch with an open and closed condition. The switch includes a movable contact that is movable from an open position to a closed position. The switch also includes a mechanism, such as a spring, for biasing this movable contact towards the closed position. Thixotropic material in the switch is positioned so that it prevents the movable contact from moving to the closed position while the material is in its first state, keeping the switch in its open condition. When the material is subjected to acceleration forces, the material changes to its second state and allows the movable contact to move to its closed position, where the movable contact provides a conductive path for the switch to change to its closed conductive condition.
Another embodiment of the invention is a normally-closed electrical switch with a movable contact that is movable from a closed position to an open position. While in the closed position, the movable contact provides a conductive path for the switch to remain in the closed conductive condition. The switch also includes a mechanism, such as a spring, for biasing the movable contact towards the open position. Thixotropic material prevents the movable contact from moving to its open position while the material is in its first state. When the material is subjected to acceleration forces the material changes to its second state and allows the movable contact to move to its open position, interrupting the conductive path between a stationary contact and the movable contact, causing the switch to change to its open non-conductive condition.
In another embodiment of the invention, a normally-open electrical switch includes electrically conductive thixotropic material. The switch also includes a reservoir for retaining this material away, and electrically isolating it from stationary contacts. While the material is in the reservoir, the switch remains in its open, non-conductive condition. When subjected to acceleration forces, the material changes to its second state and flows out of the reservoir and into electrical contact with the stationary contacts, where the material itself provides the conductive path for the switch to change to its closed conductive condition.
In yet, another embodiment of the invention a normally-closed electrical switch includes conductive thixotropic material. The material provides a conductive path between stationary contacts, keeping the switch in its closed, conductive condition while the material is in its first state. When subjected to acceleration force, the material changes to its second state and flows out of contact with the stationary contacts, interrupting the conductive path and causing the switch to change to its open, non-conductive condition.
Another embodiment of the invention is a normally closed fluidic switch that changes from a closed, non-fluid flowing condition to an open fluid flowing condition. The switch includes a thixotropic material which is positioned in a tube, such that a fluid is prevented from flowing through the tube while the material is in its first state, keeping the switch in its closed condition. When the material is subjected to acceleration forces, the material changes to its second state and flows out of the tube and into a reservoir, allowing the fluid to flow freely through the tube and causing the switch to change to its open condition.
Yet, another embodiment of the invention is a normally open, magnetic switch with a magnetic sensor and a movable magnet that is movable from a first position to a second position. The switch also includes a mechanism, such as a spring, for biasing the movable magnet towards the second position. Thixotropic material is also included in this switch and is positioned so that it prevents the movable magnet from moving to the second position while the material is in its first state, keeping the switch in its open condition. When the material is subjected to acceleration forces, the material changes to its second state and allows the movable magnet to move to its second position where it is detectable by the magnetic sensor, causing the switch to change to its second condition.
Still, another embodiment of the current invention is a normally closed magnetic switch with a magnetic sensor and a movable magnet that is movable from a first position to a second position. The switch also includes a mechanism, such as a spring, for biasing the movable magnet towards the second position. The switch further includes thixotropic material positioned so that it prevents the movable magnet from moving to the second position while the material is in its first state, keeping the switch in its second condition. When the material is subjected to acceleration forces the material changes to its second state and allows the movable magnet to move to its open position where the magnet is not detectable by the magnetic sensor, causing the switch to change to its open condition.
Another embodiment of the invention is a capacitive switch that has a first and second condition, where the capacitance of the switch is higher in the second condition than it is in the first. The switch includes first and second spaced conductive plates. The second conductive plate is movable from a first position to a second position where the second plate is spaced closer to the first plate in the second position than it is in the first position. The switch also includes a mechanism, such as a spring, for biasing the second conductive plate towards its second position. The switch also includes thixotropic material, disposed so that it prevents the second conductive plate from moving to its second position while the material is in its first state, keeping the switch in its first condition. When the material is subjected to acceleration forces, the material changes to its second state and allows the second conductive plate to move to its second position changing the switch to its second condition.
Another embodiment of the invention is a capacitive switch that has a first and second condition, where the capacitance of the switch is lower in the second condition than it is in the first. The switch includes first and second spaced, conductive plates. The second conductive plate is movable from a first position to a second position where the second plate is spaced farther from the first plate in the second position than it is in the first. The switch also includes a mechanism, such as a spring, for biasing the second conductive plate towards its second position. The switch further includes the previously described thixotropic material, disposed so that it prevents the second conductive plate from moving to its second position while the material is in its first state, keeping the switch in its first condition. When the material is subjected to acceleration forces, the material changes to its second state and allows the second conductive plate to move to its second position changing the switch to its second condition.
Another embodiment of the invention is a capacitive switch that has a first and second condition, where the capacitance of the switch is higher in the second condition than it is in the first. The switch includes first and second spaced, conductive plates. The switch includes thixotropic material that has the property of being substantially non-conductive. The material is disposed in a first location, between the plates, while the material is in its first state, keeping the switch in its first condition. When the material is subjected to acceleration forces the material changes to its second state and flows to a second location, outside of the conductive plates, changing the switch to its second condition.
Another embodiment of the invention is a capacitive switch that has a first and second condition, where the capacitance of the switch is lower in the second condition than it is in the first. The switch includes a first and second conductive plate facing and spaced apart. The switch also includes non-conductive thixotropic material. The switch further includes a reservoir for retaining the material outside of the conductive plates while the material is in its first state, keeping the switch in its first condition. When the material is subjected to acceleration forces the material changes to its second state and flows out of the reservoir and to a location between the conductive plates, changing the switch to its second condition.
An advantage of the switch is that it is non-reversible. That is, once the switch changes conditions, it would require significant effort to reset the switch. Therefore, the switch may be used in a fuse or anti-fuse application.
Another advantage is that the switch changes conditions without the use of electrical power, making it useful in applications deployed in remote or inaccessible locations.
Still, another advantage of the switch is that the switch may be made by micro fabrication techniques, significantly reducing size, weight, and cost over modern acceleration responsive switches.
The previously summarized features and advantages along with other aspects of the present invention will become clearer upon review of the following specification taken together with the included drawings.